In one technology, there is a steering control apparatus for turning the turning wheels via the turning motor at a target turning angle in response to the operation of the steering operation element (i.e., steering wheel), with the torque transmission path between the steering operation element and the turning wheels being mechanically decoupled. Such a steering control apparatus is an apparatus configuring a system (i.e., SBW system) generally called Steer By Wire (hereinafter, sometimes referred to as “SBW”).
The SBW system includes a backup clutch to mechanically couple the torque transmission path at the timing of a system failure time or system off. In order to diagnose the state of the above-described backup clutch, the engagement or release of the backup clutch needs to be done frequently, but an operation sound is generated at the time of the engagement or release of the backup clutch. For this reason, for example, JP 2010-221918 A proposes a technique of starting the diagnosis of the backup clutch, when it is detected that a vehicle driver is not in the vehicle.